The present invention relates to a method for monitoring that a plurality of mutually subsequent signals have substantially the same appearance and, thereby, are substantially alike, and for triggering an alarm and/or stop function on signal loss and/or the occurrence of one or more unknown and unacceptable deviations in the monitored signal, and for preventing triggering of an alarm and/or stop function on the occurrence of one or more known and acceptable deviations in the appearance of the monitored signal. The present invention further relates to an apparatus for carrying out the method.
In many contexts, it is fraught with serious problems to monitor electric signals which correspond, for instance, to thread movements in different types of machines, such as looms, since, in the continuous signals, there may occur signal gaps which are acceptable and are to be ignored. The most common monitoring method is to monitor that the signals'continuity is not broken. Furthermore, it is extremely difficult to pinpoint the occurrence of one or more signal gaps in the otherwise continuous signal, since this gap or these gaps do not always occur at the same position in the signal, but instead the occurrence of the signal gap or gaps has proved to be dependent on such factors as machine type, thread variety, thread quality etc. This has led to extremely complicated adjustment and fine-tuning problems, as well as extensive post-installation adjustments.